diff options
Diffstat (limited to 'docs/ref/models/fields.txt')
| -rw-r--r-- | docs/ref/models/fields.txt | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt index 27b87c1f53..344cc45280 100644 --- a/docs/ref/models/fields.txt +++ b/docs/ref/models/fields.txt @@ -351,6 +351,38 @@ looking at your Django code. For example:: db_comment="Date and time when the article was published", ) +``db_default`` +-------------- + +.. versionadded:: 5.0 + +.. attribute:: Field.db_default + +The database-computed default value for this field. This can be a literal value +or a database function, such as :class:`~django.db.models.functions.Now`:: + + created = models.DateTimeField(db_default=Now()) + +More complex expressions can be used, as long as they are made from literals +and database functions:: + + month_due = models.DateField( + db_default=TruncMonth( + Now() + timedelta(days=90), + output_field=models.DateField(), + ) + ) + +Database defaults cannot reference other fields or models. For example, this is +invalid:: + + end = models.IntegerField(db_default=F("start") + 50) + +If both ``db_default`` and :attr:`Field.default` are set, ``default`` will take +precedence when creating instances in Python code. ``db_default`` will still be +set at the database level and will be used when inserting rows outside of the +ORM or when adding a new field in a migration. + ``db_index`` ------------ @@ -408,6 +440,9 @@ The default value is used when new model instances are created and a value isn't provided for the field. When the field is a primary key, the default is also used when the field is set to ``None``. +The default value can also be set at the database level with +:attr:`Field.db_default`. + ``editable`` ------------ |